The invention pertains to a ceramic/metal substrate.
Ceramic/metal substrates are known, especially ceramic/copper substrates. These substrates are used for the manufacture of electric or electronic circuits, especially electric or electronic power circuits, and form the xe2x80x9cprinted boardsxe2x80x9d for these.
In the simplest case, such substrates have a ceramic layer that is provided with metalization on both surfaces, of which for example the metalization on the top of the ceramic layer is textured or structured in such a way, for example by using an etching process. The metalization then forms the conductors, contact surfaces etc. required for the switching circuit.
For the efficient production of electric or electronic circuits, a composite or multiple substrate (DE-PS 43 19 944) is known, in which at least two single substrates that are connected to each other as one piece are integrally formed on a large-format ceramic plate or layer. They are provided with at least one metal surface on at least one surface of the ceramic layer and connect by means of at least one predetermined break line in the ceramic layer. The separation of the composite substrate into the single substrates takes place on these predetermined break lines after applying of the electric or electronic components, by means of breaking. The disadvantage of this is thatxe2x80x94due to internal tensions in the ceramic/metal substrate that result from the temperatures arising when applying the metalization sand due to the different thermal expansion coefficients of ceramic and metalxe2x80x94uncontrolled fractures, separation or breakage can occur. Although such uncontrolled breaks occur in only 1 to 5% of all cases, the resulting loss of production and damage is not inconsiderable, especially when the separation into the single substrates does not take place until after assembly.
The application of the metalization takes place in a heat process, i.e., in a process using considerable temperatures. Thus it is known, for example, that the metalization required for electric conductors, connections etc. on ceramic, e.g. on aluminum-oxide ceramic is produced by means of the so-called xe2x80x9cDCB processxe2x80x9d (direct copper bond technology), using metal or copper foils or metal or copper sheets forming the metalization that have a layer or a coating (melt-on layer) consisting of a chemical compound of the metal and a reactive gas, preferably oxygen. In this process, which is described for example in U.S. Pat. No. 37,44,120 or DE-PS 23 19 854, this layer or coating (melt-on layer) forms an eutectic system with a melting temperature under the melting temperature of the metal (e.g. copper), so that by application of the foil on the ceramic and by heating all layers these can be connected to each other, by melting on the metal or copper in the area of the melt-on layer or oxide layer.
This DCB technology then has the following processing stages:
Oxidation of a copper foil in such a manner that an even copper oxide layer is formed;
Application of the copper foil to the ceramic layer;
Heating of the compound to a processing temperature between approximately 1065 and 1083xc2x0 C., e.g. to approx. 1071xc2x0 C.;
Cooling to room temperature.
The object of the invention is to avoid this disadvantage.
Surprisingly, random or controlled breaks can be reduced considerably (proven up to 75%) when separating the ceramic/metal substrate with the embodiment according to the present invention.